This invention relates in general to systems for filling and capping containers. In particular, this invention relates to an improved apparatus for applying threaded plastic closures formed having tamper evident bands which inhibit the application of such closures to the containers.
Many systems are known for filling containers with a product, such as a liquid, and for applying closures thereto. Typically, the containers are embodied as glass or plastic bottles having reduced diameter threaded neck portions, and the closures are embodied as threaded plastic or similar closures. Empty containers are sequentially fed through a filling machine, wherein they are filled with the product. Then, the filled containers are fed through a capping machine, wherein the closures are applied thereto. The capping machine includes both a closure application mechanism (for loosely depositing the closures on the containers) and a closure tightening mechanism (for rotating the closures relative to the containers to secure them thereon). Closure application and tightening mechanisms are well known in the art and have functioned satisfactorily with many standard closures.
More recently, however, there has been an emphasis placed on utilizing closures which have bands or similar structures formed thereon which provide a visual indication of unauthorized tampering. It has been found that the tamper evident structure formed on the closure makes it more difficult to thread the closure onto the container. Thus, many capping machines are now provided with a closure pre-tightening mechanism disposed between the closure application mechanism and the closure tightening mechanism. These pre-tightening mechanisms are adapted to tightly engage the loosely deposited closure and rotate it a small amount relative to the container to insure that the mating threaded portions thereof properly engage one another. Once this has occurred, the container carrying the pre-tightened closure is fed to the closure tightening mechanism for final tightening.
Closure pre-tightening mechanisms are known in the art. However, as more sophisticated tamper evident closure structures have been developed, it has been found that they further resist pre-tightening rotation relative to the containers. Specifically, such closures have increased band engagement beneath the annular bead on the neck of the container. The flange is more rigid and has a greatly reduced inner diameter which interferes with the container finish and makes the threaded engagement during the pre-tightening portion of the system more difficult. Thus, existing closure pre-tightening mechanisms are unable to adequately perform their intended function with these newer closures.
It has been found to be unsatisfactory to simply increase the magnitude of the frictional engagement exerted by known closure pre-tightening mechanisms to overcome the problems associated with the newer closures. This is because the greater forces applied to the outer surfaces of the closures tend to scrape or otherwise mar such surfaces with undesirable marks. Also, such forces will tilt the container, thus preventing the closure from becoming properly threaded thereon. Thus, it would be desirable to provide an improved structure for a closure pre-tightening mechanism for a container filling and capping machine which is capable for use with more sophisticated tamper evident closure structures.